The present invention relates to a method and apparatus for adjusting the operating bandwidth in a radiotelephone for operation in a plurality of radiotelephone systems.
Radiotelephones, and more particularly cellular radiotelephones, typically operate on only one type of cellular telephone system, for instance, the European GSM (Groupe Special Mobile) or the proposed U.S. system. Prior art telephones that are capable of use in different radiotelephone systems have been equipped with multiple transceivers. U.S. Pat. No. 4,972,455 permits use of different systems by using a transceiver having a dual bandwidth receiver with different filters in the intermediate frequency (IF) section. The filters have different bandwidths and are switchably selected, depending on which cellular service is available. This patent discloses two fixed filters which limit the use of the radiotelephone to systems and applications determined by the selected filter characteristics. Switches may also give rise to crosstalk effects. Thus, there is felt a need for a radiotelephone with a more flexible selection of the operating characteristics.